Method for the routing of IP frames between the users of a variable graph network

ABSTRACT

Disclosed is a virtual router distributed on a carrier network, said carrier network comprising one or more components, each of the components comprising at least two nodes communicating with one another by means of an artery, a node comprising a FAx access function and server functions (LES/BUS, LECS, MPS). At least one component of said network comprises the following elements:  
     several ELANi-bridges, each ELANi-bridge being connected to a virtual network VLANi,  
     at least one transit ELAN, Tx,  
     at the level of an access function Fax,  
     LEC router means Rix adapted to connecting the access function FAx to at least one ELANi associated with a VLANi,  
     means (Lx) for the identification of the VLANi serviced by the access function FAx,  
     means (LEC transit) to connect the transit ELAN to the access function.  
     Use of a distributed virtual router ATM type carrier networks and IP data packets.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a virtual router distributedover a carrier network and a method for the routing of packets amongseveral virtual local area networks relying on a switching network whosegraph may be variable owing to the mobility of its nodes.

[0003] The expression “distributed virtual router” is used to designatethe routing method. The underlying switching network is also known as a“carrier network”.

[0004] The nodes of the network communicate with one another for exampleby means of arteries whose configuration or existence may evolve overtime, leading to a mobility of the nodes.

[0005] The invention can be applied especially to IP format packets ofthe Internet protocol.

[0006] The present invention can be applied for example in ATM typenetworks.

[0007] It can be applied to the emulation of routing in all networksusing switching techniques.

[0008] 2. Description of the Prior Art

[0009] In the prior art, the routing is done by means of a piece ofequipment known as a router that relays the packets entering a junctorof this equipment towards an output junctor as a function of thedestination IP address of the packet and as a function of the routingtable.

[0010] When the routing is done between a large number of local areanetworks at very great distances from one another, a meshed network ofrouters consisting of access routers and transit routers is generallyused.

[0011] A configuration of this kind has certain drawbacks, especiallythe following ones:

[0012] 1) the transit time of a packet in the network is adverselyaffected by the large number of routers to be crossed,

[0013] 2) the notion of quality of service (QoS) is not taken intoaccount.

[0014] One way to overcome the above-mentioned drawbacks consists forexample in integrating the IP routing (level 3) with a switchingtechnology (level 2) such as the ATM (asynchronous transfer mode)switching. Three lines of development have been emphasized.

[0015] For example, what is called the gigarouter technology achieves arouting function at the core of a switch in taking account of thedestination IP address in the switching process. In the ATM context, thedestination IP address is taken into account during the translation oflogic channels.

[0016] The label-switching technology identifies the flows within the IPtraffic by a process of signalling associated with these flows of labelsused by the level 2 switching. Applied to the ATM, a logic pathindicator VPI/VCI is associated with a flow. This technology is beingstandardized at the IETF under the name of multiprotocol label switching(MPLS).

[0017] The technology known as “local area network and routingemulation” is used to create virtual circuits that directly connect thecommunications applications (short circuits) in using a specificprotocol that defines customer entities, server entities, connectionsbetween these entities and rules for making short circuits betweencustomers. In the ATM context, this technology is covered by a standardknown as local area network emulation (LANE) and multiprotocol over ATMor MPOA.

[0018] This technology relies on the implementation of essentialcentralized functions of servers, flow routers with short lifetimescapable of being duplicated or even triplicated to provide minimumredundancy. However, when the network is subdivided into severalnon-interconnected components, there is no certainty that each componentwill have all the functions essential to the service nor that when twonetworks are combined, the redundant functions (offered by each of thecomponents taken individually) will merge harmoniously, namelytransparently for the user.

[0019] The object of the invention relates especially to a method ofrouting between virtual local area networks when the underlyingswitching network has a graph that may be variable owing to the mobilityof its nodes, the network possibly being constituted by severalcomponents. A component is defined as a sub-network comprising at leasttwo nodes that communicate with each other by arteries.

[0020] The number of components may be equal to the numbers of switchesof the network.

SUMMARY OF THE INVENTION

[0021] The invention relates to a virtual router distributed on acarrier network, said carrier network comprising one or more components,each of the components comprising at least two nodes communicating withone another by means of an artery, a node comprising a FAx accessfunction and server functions (LES/BUS, LECS, MPS). It is characterizedin that at least one component of said network comprises the followingelements:

[0022] several ELANi-bridges, each ELANi-bridge being connected to avirtual network VLANi,

[0023] at least one transit ELAN, Tx,

[0024] at the level of an access function FAx:

[0025] router LEC means Rix adapted to connecting the access functionFax to at least one ELANi associated with a VLANi,

[0026] means (Lx) for the identification of the VLANi serviced by theaccess function FAx,

[0027] means (LEC transit) to connect the ELAN transit to the accessfunction.

[0028] The invention also relates to a method of routing in a switchednetwork comprising one or more components, the component or componentscomprising at least two nodes connected by a communications artery, eachof the nodes comprising an access function FAx. It is characterized inthat it comprises at least one step where the access function relays thedata packets received on one of the LECs as follows:

[0029] (a) if the addressee of the packet is an internal routingfunction laid out at a node X, the packet is directly handed over tosaid function,

[0030] (b) if the addressee of a packet is a VLAN serviced by the FAxaccess function, the data packet is relayed to the router having thesame identifier,

[0031] (c) if the addressee of the packet is a VLAN that is notserviced, the packet is relayed to the transit ELAN.

[0032] The step (b) may be carried out as follows:

[0033] if the addressee VLAN with the identifier j belongs to the listLx, the relaying function of FAx is activated and the data packet isrelayed to the LEC router Rjx having an identifier that is theidentifier of the addressee VLAN, and

[0034] the step (c) may be carried out as follows:

[0035] if the addressee VLAN does not belong to the list Lx, the datapacket is relayed to the transit LEC mentioned in the routing table.

[0036] The use of the virtual router distributed to ATM type supportingnetworks and IP data packets or IP frame between the users of a variablegraph network for example.

[0037] The present invention comprises especially the followingadvantages:

[0038] it provides users of non-interconnected components with a routingservice equivalent to the one offered by the complete network,

[0039] in the case of the merger of several components, it enables themerger without redundancy of the functions offered.

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Other features and advantages of the invention shall appear fromthe following description given by way of an illustration that in no wayrestricts the scope of the invention, with reference to the appendedfigures, of which:

[0041]FIG. 1 shows a general view of a network,

[0042]FIG. 2 shows a general view of the network of FIG. 1 aftersplitting into two components,

[0043]FIG. 3 shows an architecture of a switch according to theinvention,

[0044]FIG. 4 shows an IP access function according to the invention,

[0045]FIG. 5 shows an exemplary architecture of a distributed virtualrouter according to the invention, and

[0046]FIG. 6 is an architecture of a router after the splitting of thearchitecture described in FIG. 5.

MORE DETAILED DESCRIPTION

[0047] The method according to the invention or “distributed virtualrouter” is designed especially to offer a routing service among severalvirtual local area networks or VLANs relying on a switching networkwhose graph is variable owing to the mobility of its nodes.

[0048] Indeed, in the course of time, the switching network is capableof getting split up into numerous non-interconnected components, acomponent being formed for example by several nodes communicating bymeans of arteries, and/or of getting extended by the interconnection ofsuch components. At the most, the splitting up of a network may lead toa number of components equal to the number of switches or nodes of thenetwork.

[0049] The description given here below by way of a non-restrictedillustration relates to an ATM support network and can be applied to theemulation of IP packet routing. It can also be used in all networksimplementing other switching and routing technologies.

[0050]FIG. 1 shows a view of an ATM network 1 (level 2) comprisingseveral switches 2 (corresponding for example to the nodes X, Y and Z ofthe network) and several arteries 3, each of the arteries connecting twoswitches. This network has the function especially of interconnectingdifferent items of equipment 4 in local area network emulation mode.These different items of equipment 4 fulfill the role of passagewaysbetween several ethernet networks 5, referenced Ui, Vi, Uj and Vk towhich they are connected and the ATM network 1. Various stations can beconnected to each ethernet network.

[0051] An ethernet network designated by an identifier i, j, . . . isconnected to a VLAN designated by the same identifier.

[0052] Thus, in the example of FIG. 1, the networks Ui and Vi correspondto the same VLANi, the networks Uj to the VLANj and the networks Uk, Vkto the VLANk.

[0053] The network ATM 1 provides a bridge service according to theprior art, for example between the different networks belonging to oneand the same VLAN and a routing service according to the invention, forexample between the three VLAN networks VLANi, VLANj and VLANk.

[0054]FIG. 2 shows a network comprising elements identical to thosedescribed in FIG. 1 and having the same references, wherein the node Xis isolated from the rest of the network. The nodes Y and Z areconnected by a communications artery 3. The network has two components,a first component comprising the node X that is insulated and a secondcomponent comprising the two nodes X and Y and the communications artery3.

[0055] The object of the invention especially is to propose an adaptedswitch architecture to provide intercommunication services between thenetworks within each component, namely the routing between Ui and Vk inthe first component and the routing between Vi, Uj and Uk in the secondcomponent.

[0056] The switch 2 described in detail in FIG. 3 comprises for example:

[0057] an access function IP 20 according to the invention described indetail in FIG. 4,

[0058] a LES/BUS (LAN emulation server/broadcast or unknown server)function 21,

[0059] a LECS (LAN emulation configuration server) function 22, and anMPS (MPOA server) function 23.

[0060] The latter three functions are designated in the description forreasons of simplification by the expression “server function” and havecharacteristics known in the prior art.

[0061]FIG. 4 gives a detailed view of an exemplary embodiment of a IPaccess function 20 implanted in a node and having characteristicsaccording to the invention.

[0062] This IP access function 20, referenced by the acronym FAx wherethe index x corresponds to the node concerned, in this case the node X,comprises for example:

[0063] a transit LEC 201 referenced Tx having the index of the nodeconcerned, LEC being the abbreviation of LAN emulation client,

[0064] n router LECs 202 referenced Rix where n is the number of VLANs,i corresponding to the identifier of the VLAN and x to the index of thenode concerned,

[0065] a relaying function 203 that receives the IP packet and processesit as a function of its header; for example it modifies the header andre-sends the packet,

[0066] a routing table 204 containing the routing data,

[0067] a routing function 205,

[0068] an election function 206 used to assign the servicing of eachVLAN to a single access function, and a list Lx 207 of VLANs serviced.

[0069] These different elements and their interactions with the networkare explained here below.

[0070] Transit LEC 201

[0071] The ATM support network comprises for example an emulated LAN(ELAN) known as a transit ELAN for which all the IP access functions areclients by means of a LEC function known as a “LEC transit”. Forexample, the transit LEC function of the access function of the node Xis referenced LEC Tx. Those of the nodes Y and Z are respectivelyreferenced LEC Ty and LEC Tz. The transit LEC is connected to thetransit ELAN.

[0072] Router LEC 202

[0073] Each VLAN has an associated single emulated LAN in the carriernetwork. This LAN is called a bridge ELAN. All its access functions areclients by means of a LEC function (LAN emulation client) called arouter LEC. A bridge ELAN is designated like the VLANs by an identifieri, j, . . .

[0074] For example, the IP access function FAx of the node X is a clientof each bridge ELAN, ELANi associated with the VLANi by means of therouter LEC Rix.

[0075] Lx list 207

[0076] This list has the function especially of identifying the VLANsserviced by the access function FAx.

[0077] The constitution of a list Lx is performed for example asfollows: for a given component of a network comprising m nodes having anidentifier x, y, . . . and therefore m lists Lm, the intersection anytwo of the lists Lm corresponds to the empty set.

[0078] In the example given in FIGS. 1 and 5 where the component of thenetwork considered has three nodes referenced X, Y and Z, thecorresponding lists Lx, Ly and Lz are determined so that when one ofthem takes any two of the three lists, their intersection is equal to φ.In this example, for the node X, Lx={i, j}, for the node Y, Ly={k} andfor the node Z, Lz={}.

[0079] It is possible to use an election protocol known to those skilledin the art, for example the VRRP protocol standardized at IETF underreference RFC 2338.

[0080] The implementation of the election protocol is for exampleensured by the election function 206 implanted in each access functionFAx, FAy, FAz and engaging in dialog with the corresponding functions ofthe other nodes forming part of the same component of the network, byexchange of packets on the bridge ELANs through the router LECs Rixmentioned.

[0081] Routing and relaying functions and the routing table

[0082] The IP access functions, FAx, FAy . . . implement a routingfunction and a relaying function as well as a routing table known in theprior art.

[0083] The routing function 205 sustains a routing table 204 by means ofa dialog with the homologous routing functions through a routingprotocol.

[0084] The relaying function 203 enables the relaying of any packetcoming from an ELAN towards another ELAN as a function of itsdestination IP address and of the information contained in the routingtable.

[0085] From the routing point of view, all the IP access functions ofone and the same component are adjacent through the transit ELAN. Therouting protocol uses the transit ELAN to broadcast the routinginformation to the corresponding units towards the bridge ELANs, ELANi,ELANj, . . . where i, j belong to the Lx lists defined, using theprinciple mentioned here above, through the associated router LECs.

[0086] A principle of implementation of an access function implanted inthe node, for example FAx implanted in the node X, may be as follows:

[0087] The access function IP FAx relays for example all the IP packetsreceived on the router LECs, LEC Rix where i belongs to Lx on the basisof the destination IP address and the information contained in therouting table.

[0088] If the destination of the IP packet is a function internal to theaccess function FAx, such as the election function or the routingfunction, the IP packet is forwarded directly to this internal function.

[0089] Else.

[0090] If the destination VLAN j for example belongs to the list Lx ofthe addressee VLANs, the access function FAx activates its relayingfunction 203 in order to relay the IP packet to the router LEC Rjx ofthe node x linked with the ELAN j connected to the VLANj.

[0091] If the destination VLAN j does not belong to the list Lx, it isnot part of the VLANs serviced by the node X, the IP packet is relayedto the transit LEC Tx which sends it on the transit ELAN towards atransit LEC indicated in the routing table (known by the expression“next hop”) for example Ty, the transit LEC of the node Y.

[0092] The router LECs Rmx of the node x where the identifier m does notbelong to the list Lx remain inactive, for example Rkx in FIG. 5. Inthis case, only the destination packets IP of the internal electionfunction are accepted.

[0093] The access function FAx also relays all the packets IP receivedon the transit LEC Tx by using the destination address IP and theinformation contained in the routing table.

[0094] If the addressee of the IP packet is the internal routingfunction 205 laid out in the node X, the IP packet is forwarded directlyto this function.

[0095] If the packet is destined for a VLANi serviced by the accessfunction FAx, namely it belongs to the list Lx, the packet is relayed tothe router LEC of the access function having an identifier index i ofthe VLAN and the index x of the node, Rix.

[0096] If the packet is intended for a VLAN not serviced by the accessfunction (the identifier i of the VLAN does not belong to the list Lx),the access function FAx relays the packet in taking account of theinformation contained in the routing table 204 to the transit ELAN.

[0097] Each VLANm having an identifier m has one or more points ofaccess to the routing service by means of LEC functions of thecorresponding bridge ELAN, ELANm, associated with the VLANm. These LECfunctions are named “user LEC”.

[0098] For example, the VLANi has several LECs designated by LEC Ui, LECVi that are physically connected to any nodes of the carrier network,these LECs forming part of the bridge ELAN having an identifier i.

[0099] Certain user LECs could be internal to a node of the network whenthis network provides ethernet access.

[0100] Short circuits enabling the exchange of data flows forsufficiently lengthy periods are automatically set up by MPOA(multiprotocol over ATM).

[0101]FIG. 5 gives an exemplary view of an architecture of thedistributed virtual router according to the invention in a component ofthe network.

[0102] The distributed virtual routing function is achieved for exampleby a community of several IP access functions 20 referenced FAx, FAy,FAz, . . . connected to one another in local area network emulation by atransit ELAN 8 and by n bridge ELANs 9 designated ELANi, ELANj, ELANkwhere n is the number of VLANs and i is the identifier of a VLAN.

[0103] In each switch for example the switch X, the transit LEC Tx isconnected to the transit ELAN 8 and the router LECs Rix, Rjx, Rkx areeach connected to a corresponding bridge ELAN ELANi, ELANj, ELANk.

[0104] For the switch Y, the transit LEC is connected to the transitELAN 8 and each router LEC is connected to the corresponding ELAN Riy atELANi, Rjy at ELANj, Rky at ELANk.

[0105] For the switch Z, the transit LEC is connected to the transitELAN 8 and each router LEC is connected to the corresponding ELAN Riz atELANi, Rjz at ELANj, Rkz at ELANk.

[0106] The only elements activated are the router LECs Rix such that ibelongs to Lx, the list of serviced VLANs being contained in the table207 (FIG. 4).

[0107] In the example given Lx={i, j}, Ly={k} and Lz corresponds to thevacant assembly. This architecture is compatible with the networkdescribed in FIG. 1. The non-activated router LECs are designated by across Rkx, Riy, Rjy, Riz, Rjz, and Rkz.

[0108]FIG. 6 shows an exemplary architecture of the distributed virtualrouter when the network is subdivided into two components as shown inFIG. 2.

[0109] The following table describes the table of actions to beperformed upon reception of a packet of the node X.

<all except LEC Tx> Election function Forward to the election functionRix, Rjx or Tx Routing function Forward to the routing function Rix orTx User of ELAN j Relay towards Rjx Rix, Rjx or Tx User of ELAN k Relaytowards Tx (next hop Ty) Rjx or Tx User of ELAN i Relay towards Rix Inall other cases: Destroy the packet

[0110] In all the exemplary embodiments described here above, thecarrier network may be a network with level (2) according to thetechnology known to those skilled in the art.

What is claimed is:
 1. A virtual router distributed on a carrier network, said carrier network comprising one or more components, each of the components comprising at least two nodes communicating with one another by means of an artery, a node comprising a FAx access function and server functions (LES/BUS, LECS, MPS), wherein at least one component of said network comprises the following elements: several ELANi-bridges, each ELANi-bridge being connected to a virtual network VLANi, at least one transit ELAN, Tx, at the level of an access function FAx: LEC router means Rix adapted to connecting the access function FAx to at least one ELANi associated with a VLANi, means (Lx) for the identification of the VLANi serviced by the access function FAx, means (LEC transit) to connect the transit ELAN to the access function.
 2. A distributed router according to claim 1, wherein the step of determining the lists of the serviced VLANi is obtained by considering any one of the Lm lists and determining the contents of its intersection with any other of the lists to obtain the empty set.
 3. A router according to claim 2, wherein a list Lm is drawn up by using an election protocol such as the VRRP protocol standardized at the IETF.
 4. A router according to one of the claims 2 or 3, comprising an election function implanted in the access function FAx engaged in dialog with the homologous functions by exchange on the ELANi bridges in using the LEC routers Rix.
 5. A router according to one of the above claims, wherein a VLAN comprises at least one <<LEC user >> connected to a node of the carrier network.
 6. A router according to the above claim, wherein the <<LEC user >> function is implanted in a node of the carrier network for ethernet type access operations.
 7. A router according to one of the claims 1 to 6, distributed in ATM type carrier networks with IP type data packets.
 8. A method of routing in a switched network comprising one or more components, the component or components comprising at least two nodes connected by a communications artery, each of the nodes comprising an access function FAx, wherein the method comprises at least one step where the access function relays the data packets received on one of the LECs as follows: (a) if the addressee of the packet is an internal routing function laid out at a node X, the packet is directly handed over to said function, (b) if the addressee of a packet is a VLAN serviced by the FAx access function, the data packet is relayed to the router having the same identifier, (c) if the addressee of the packet is a VLAN that is not serviced, the packet is relayed to the transit ELAN.
 9. A routing method according to the above claim 8, wherein the step (b) is carried out as follows: if the addressee VLAN with the identifier j belongs to the list Lx, the relaying function of FAx is activated and the data packet is relayed to the LEC router Rjx having an identifier that is the identifier of the addressee VLAN, and the step (c) is carried out as follows: if the addressee VLAN does not belong to the list Lx, the data packet is relayed to the transit LEC mentioned in the routing table.
 10. A routing method according to one of the claims 8 and 9, wherein the relaying step is performed for a data packet received on the router LEC implanted in an access function.
 11. A method according to one of the claims 8 and 9 wherein the relaying step is achieved for a data packet received on the transit LEC of the component of the network.
 12. A routing method according to one of the claims 8 to 11 using an ATM type carrier network and IP data packets. 